Saving RM45K on agent fees for a RM400K condo is a very good deal. Just get a lawyer to advise you on the process. Yes, the document you signed will be legally binding, it's no different compared to engaging an agent.

Since you need to engage a lawyer anyway, it will be better if you get the lawyer to draft the agreement for you.

This really depends on individual, MLTA is basically life insurance in disguise, if you plan to settle your loan sooner, MRTA will be a better option. Check out this article for more info: https://www.imoney.my/articles/mrta-vs-mlta-need

Note: If you are applying your housing loan through a mortgage broker who often double as insurance agent, they will try to push MLTA to you, if you apply your loan directly with bank, bank officer will try to push MRTA to you. So you really need to decide for yourself which is better for you.